High-speed, multi-Z confocal microscopy for voltage imaging in densely labeled neuronal populations

Genetically encoded voltage indicators (GEVIs) hold great promise for monitoring neuronal population activity, but GEVI imaging in dense neuronal populations remains difficult due to a lack of contrast and/or speed. To address this challenge, we developed a novel confocal microscope that allows simultaneous multiplane imaging with high-contrast at near-kHz rates. This approach enables high signal-to-noise ratio voltage imaging in densely labeled populations and minimizes optical crosstalk during concurrent optogenetic photostimulation.

High performance InGaAs/InP avalanche photodiode integrated with metal-insulator-metal microcavity

Reducing the dark current of InGaAs/InP avalanche photodiodes (APDs) is an important way to improve its performance. Decreasing the active size can reduce the dark current but sacrifice the quantum efficiency. In this paper, the Metal-Insulator-Metal (MIM) microcavity is integrated with an APD, which can converge light from tens of microns to several microns, to compensate for the loss of detection efficiency caused by the reduction of the size of the APD. Through photoelectric joint simulation, the optical response of the device can be obtained, and the coupling effect between the MIM structure and the APD can be analyzed directly. The simulation results show that the signal to noise ratio of the APD integrated with the MIM microcavity is twice of the MIM free traditional APD, and the 3dB bandwidth reaches 5.8 GHz. When the MIM microcavity is applied to an APD array, the optical crosstalk between pixels is found to be negligible.